The present invention generally relates to the field of engine control systems which provide control signals for controlling engine cylinder apparatus associated with each cylinder of a three or more cylinder engine. More particularly, the present invention relates to an engine control system which includes an improved cylinder identification apparatus to insure the proper sequential routing of engine control signals to control apparatus associated with each cylinder of a three or more cylinder engine.
Analog and digital engine control systems which develop electronic control signals for controlling engine functions are known and an example of such an analog system is illustrated in U.S. Pat. No. 4,104,997 to Kenneth Padgitt, entitled "Multiple Slope Ignition Spark Timing Circuit", whereas an example of a digital engine control system is illustrated in U.S. Pat. No. 4,231,332 to Robert Wrathall, entitled "Spark and Dwell Ignition Control System Using Digital Circuitry", both of the preceding U.S. patents being assigned to the same assignee as the present invention. In both of the aforementioned U.S. patents, engine position sensors are utilized to provide sensor pulses indicative of engine crankshaft position and speed and control circuits are disclosed which process these sensor pulses to provide control signals to control the dwell and spark occurrence functions for each of the engine cylinders. In the Wrathall '332 patent, a two-cylinder engine control system is disclosed wherein a combination dwell and spark occurrence control signal is utilized to simultaneously provide control excitation for a single pair of engine cylinders. The aforementioned Padgitt '997 patent illustrates an analog system wherein an additional sensor is utilized solely for the purpose of determining the sequence in which two pairs of engine cylinders (in a four-cylinder engine) should receive a composite dwell and spark timing signal.
Generally, when the engine functions of more than two cylinders of an engine must be controlled, it is necessary to distinguish between a plurality of various sensor pulses produced by each sensor during each revolution of the engine crankshaft such that the functions of the engine cylinders will be controlled in the proper sequence with each cylinder receiving a control signal while the cylinder piston is at a proper compression and/or exhaust cycle position with respect to the engine crankshaft rotational position. In the Padgitt '997 patent this is accomplished through the use of an additional sensor whose sole function is to distinguish between different half cycles of revolution of the engine crankshaft. Since sensors are costly as compared with other electronic circuitry, while the Padgitt patent provides a feasible solution to identifying whether ignition control sensor pulses are associated with one or another half cycles of the engine crankshaft rotary position, this solution is not cost effective.
Other types of engine cylinder identification apparatus have also utilized additional sensors for the sole purpose of distinguishing between various portions of the revolution cycle of the engine crankshaft, and therefore these systems suffer from the same cost problems as the Padgitt '997 patent.
Typically, the prior systems which utilize sensors to provide cylinder identification information have been unable to block sensor outputs during spark occurrence. The result is that erroneous cylinder identification is possible since during spark creation the sensor may produce false output pulses.
While the Wrathall '332 U.S. patent provides a cost effective spark and dwell control system for a two-cylinder engine, expanding this system to a four-cylinder engine according to the teachings of the prior art would generally involve the use of an additional sensor to provide additional information to the control system so as to properly route the engine control signals to the proper engine cylinders in the proper sequence.
While the discussed systems relate to the production of engine dwell and spark timing control signals, the same problem exists for engine fuel injection systems wherein the routing of an electronically generated fuel injection control signal to the proper engine cylinder fuel injectors may require an additional sensor merely to provide additional engine crankshaft rotational position information to the control system so as to insure the proper sequencing of control information to the proper cylinders. Copending U.S. patent applications Ser. Nos. 183,657, to Hunninghaus et al, and 183,658, to Bolinger, both filed on Sept. 2, 1980 and both assigned to the same assignee as the present invention deal with cylinder identification systems which insure the synchronizing of fuel injection signals for four or more cylinder engine. Both of these applications illustrate how additional sensors can be utilized to provide cylinder identification information.
Some engine control systems attempt to utilize the same sensor or sensors for providing a plurality of engine position pulses for each crankshaft revolution while distinguishing between these plurality of pulses through the use of additional circuitry. These systems generally distinguish between a reference pulse duration and sensor pulses having different time durations by circuitry which makes this determination as a function of engine crankshaft speed wherein the accuracy of properly identifying which of the plurality of sensor pulses should be associated with which engine cylinder becomes a function of engine crankshaft speed. Typically, these systems distinguish between the reference pulse duration and other sensor pulse durations by use of elapsed time counting circuits, and these systems do not function at all at very low engine speeds encountered during engine start up (unless extremely large capacity counters are used), since these systems must operate properly at normal engine speeds. In addition, these systems generally utilize only a single sensor and would not be readily adaptable to the dual sensor engine control system illustrated in the Wrathall '332 patent wherein one sensor is positioned at a stationary position defining the latest dwell initiation position of the engine crankshaft for the engine cylinders whereas another stationary sensor is positioned to define the latest time occurrence of spark ignition for engine cylinders. Some systems which utilize a pair of sensors determine cylinder identification by the time coincidence of sensor pulses, but these systems are subject to false identifications due to spark causing simultaneous pulses in each sensor.